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NVAP Reference Guide: Chronic

Wasting Disease (Control and

Eradication)

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NVAP Reference Guide: Table of Contents

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Preface

Introduction

Control and Eradication

Brucellosis

Johne’s Disease

Pseudorabies (PRV)

Tuberculosis

Transmissible Spongiform Encephalopathies

Scrapie

Bovine Spongiform Encephalopathy (BSE)

Chronic Wasting Disease (CWD)
Poultry

National Poultry Improvement Plan (NPIP)

Avian Influenza (AI)

Exotic Newcastle disease (END)

Equine Disease

Aquatic Animal

Aquatic Animal National Health Plan

Aquatic Animal Health Activities

Animal Health Emergency Management

Animal Health Emergency Management

Emergency Response Structure

National Response Framework (NRF)

National Incident Management System (NIMS)

National Animal Health Emergency Management System (NAHEMS)

Foreign Animal Disease Preparedness and Response Plan (FAD PReP)

FAD Recognition and Initial Response

National Animal Health Emergency Response Corps (NAHERC)

Notifiable Diseases and Conditions

WOAH and International Standards

Cleaning and Disinfection

Importance of Cleaning & Disinfection

Cleaning

Disinfection

Regulation of Disinfectants

Safety

Disease Surveillance

Laboratory Submissions

Animal Movement

Interstate Regulations

Interstate Movement of Cattle, Horses, Swine, Sheep and Goats

Issuing Interstate Animal Movement Documents

International Animal Movement
Issuing International Health Certificates (IHCs) for Live Animal Movement

Common Problems Observed on Certificates for Live Animal Movement

Animal Identification 

Animal Identification

Cattle Identification

Swine Identification

Equine Identification

Sheep and Goat Identification

Fowl Identification

Compliance and Regulations

Appendix

A: 9 CFR PARTS 160, 161, and 162

B: APHIS VS District Offices

C: State Animal Health Officials

D: Forms

E: Other Organizational Information with Contact Points

F: Web Sites

G: Equine Teeth and Aging

CWD is a TSE of cervids in the genera Odocoileus, Cervus, and Alces. Known

susceptible species are white tailed deer, mule deer, black tailed deer, Rocky

Mountain elk, and moose. Transmission studies involving direct or indirect contact

between CWD infected deer and elk, and other ruminant species including wild

ruminants and domestic cattle, sheep, and goats have shown no evidence of

transmission of CWD to these other ruminant species. 

First recognized as a clinical “wasting” syndrome in 1967 in mule deer in a wildlife  

research facility in northern Colorado, it was identified as a TSE in 1978. CWD is

typified by chronic weight loss leading to death. There is no known relationship

between CWD and any other TSEs of animals or people. 

In the mid-1980s, CWD was first detected in free-ranging deer and elk in contiguous

portions of northeastern Colorado and southeastern Wyoming. In May 2001, CWD
also was found in free-ranging deer in the southwestern corner of Nebraska

(adjacent to Colorado and Wyoming). At that time, the limited area of northern

Colorado, southern Wyoming, and western Nebraska in which free-ranging deer and

elk positive for CWD have been found was referred to as the original endemic area. 

Since 2001, CWD has been identified in free-ranging cervid populations in 21 States:

Colorado, Illinois, Kansas, Maryland, Minnesota, North Dakota, Nebraska, New York,

New Mexico, South Dakota, Utah, Virginia, Wisconsin, West Virginia, Iowa, Michigan,

Missouri, Pennsylvania, Arkansas, Texas and Wyoming. The first CWD-positive freeranging moose was identified in Colorado in 2005. 

Since 1997, CWD has been found in farmed cervids (white-tailed deer, red deer, and

elk) in  16 States: Colorado, Kansas, Michigan, Minnesota, Missouri, Montana, New

York, Oklahoma, South Dakota, Iowa, Nebraska, Ohio, Pennsylvania, Texas, Utah and

Wisconsin.   

CWD also has been found South Korea, Norway and two Canadian provinces,

Saskatchewan and Alberta.

Like the causative agents of scrapie and Bovine Spongiform Encephalopathy (BSE),

the agent responsible for CWD has not been completely characterized. The CWD

agent is thought to be an abnormal prion protein. It is smaller than most viral

particles and does not evoke a traditional whole body immune response in the host

animal, but does cause neuroinflammation. On the basis of experience with other

TSE agents, the CWD agent is assumed to be resistant to enzymes and chemicals

that normally break down proteins as well as to heat and normal disinfection

procedures. 

Clinical Signs

CWD has been reported to occur in susceptible cervids 6 months of age and older.

The disease is progressive and always fatal. The most obvious and consistent clinical

sign of CWD is long-term weight loss with loss of body condition, as well as

increased drinking and urination. Behavioral changes also occur in the majority of

cases, including decreased interactions with other animals in the pen, aggression,

listlessness, depression, and lowering of the head. These changes may be subtle and

may not appear until late in the disease progression.
Testing

Currently, definitive diagnosis is based on IHC testing of the obex area of the brain

stem or the medial retropharyngeal lymph nodes. Gross lesions seen at necropsy

reflect the clinical signs of CWD, primarily emaciation and sometimes aspiration

pneumonia, which may be the primary (acute?) cause of death. On microscopic

examination, lesions of CWD in the central nervous system resemble those of other

spongiform encephalopathies. At this time, abnormal prion proteins can be detected

using immunohistochemistry (IHC), Western blotting, enzyme-linked immunosorbent

assay (ELISA), prion misfolding cyclic amplification (PMCA), and real-time quaking

induced conversion (RT-QuIC), however, approved diagnostic assays are limited to

IHC and ELISA. Research is being conducted to develop live-animal diagnostic tests

for CWD. The rectal biopsy test, while not yet approved for routine regulatory

testing, appears promising but may have limited applicability due the number of

positive animals in the early stages of the disease that may not be detected. 

Official CWD tests are performed only at APHIS-approved university, State, or

Federal veterinary diagnostic laboratories. If the animal to be tested is a farmed

deer or elk, accredited veterinarians should check with Federal or State regulatory

veterinarians for information on sample collection and appropriate sample

submission. If the animal to be sampled is a wild deer or elk that is suspected of

having CWD, accredited veterinarians should inform State and Federal authorities

and work with their State wildlife management agency to find out how officials would

like the sample collected and submitted.

If the animal to be sampled is a clinically normal wild animal that an individual

hunter would like tested, accredited veterinarians should also work with their State

wildlife management agency or department of agriculture to find out how best to

proceed. Several approved laboratories exist with sufficient capacity to provide feefor-service testing for samples collected by individual hunters. Accredited

veterinarians should always check with the diagnostic laboratory to make sure

samples are properly collected, packaged, and shipped. 

Disposal

Horizontal transmission of CWD has been demonstrated from environments

contaminated with CWD-positive organic materials. Therefore, the proper disposal
and decontamination of potentially CWD- infected fomites and tissues is an

important factor in reducing the risk of CWD transmission. Carcass and tissue

disposal options may be regulated by the Environmental Protection Agency (EPA),

FDA, or State or local authorities. Accredited veterinarians should check with these

entities first before attempting to decontaminate fomites or dispose of a suspect or

positive carcass. 

Management

APHIS has provided assistance to State officials in diagnosing CWD and in monitoring

international and interstate movements of animals to help prevent further spread of

CWD. An extensive nationwide surveillance effort was started in 1997–98 to better

define the geographic distribution of CWD in free-ranging cervids. 

Surveillance for CWD in farmed cervids began in 1997 and has been a cooperative

effort involving State agriculture and wildlife agencies and APHIS. Farmed cervid

surveillance has been increasing each year since 1997 and is now an integral part of

the USDA program to prevent and control CWD in farmed cervid herds and wild

cervid populations. 

In 2002, at the request of Congress, USDA and the U.S. Department of the Interior

worked with the States to create a national plan to assist States, Federal agencies,

and Indian tribes in addressing CWD in both farmed and wild animals. Unfortunately,

funding for the wildlife surveillance program was discontinued in FY2012.

USDA has continued to develop a national herd-certification program with a goal to

control and prevent the spread of CWD in farmed cervids. The program includes

requirements for fencing, animal identification, animal inventory, and continued

surveillance testing for herd advancement. After 5 years of continual surveillance

with no evidence of disease, a herd is considered to be certified and can move

animals interstate.

Learn more about CWD.